As disclosed in, for example, Patent Document 1, a variable-resistor used for a liquid level detector conventionally indicates an electric resistance value (hereinafter “resistance value”) in accordance with the level of a liquid surface by the displacement of a sliding contact relative to an insulating substrate according to the liquid surface level. In such a variable resistor, electric conductors arranged side by side along the slide locus of the sliding contact, and a resistor that connects the conductors to generate an electric resistance between these conductors are formed on the insulating substrate.